A variety of important biological redox functions are performed by copper proteins such as electron transfer proteins, oxidases, monooxygenases, and dioxygeneses. Also represented as copper proteins are the oxygen-carrying pigment, hemocyanin, and the Cu-Zn superoxide dismutase enzyme. In many of these systems (most notably the lactases, ascorbate oxidase, ceruloplasmin, dopamine-beta-hydroxylase, hemocyanin, and perhaps, superoxide dismutase) a binuclear copper center is present which either participate in the redox step or is involved as the site for interaction with dioxygen. The types in interaction which occur between copper proteins and dioxygen include reversible coordination of O2, activation of O2, and rapid reoxidation of a Cu(I) state of the enzyme. Little is known about the ability of binuclear copper complexes to act as redox centers or about the interactions of O2 with Cu(I)...Cu(I) species. Since binuclear copper centers are important in copper proteins we propose to synthesize low-molecular weight binuclear chelates and examine the basic structural and stereochemical factors which influence the redox behavior of these systems.